Collections¶

Support of fake collections has been added to Datafaker since version 1.2.0.

For example, the following code will generate a list of first and last names with number of elements in it between 3 and 5:

Java

List<String> names = 
    faker.<String>collection()
        .suppliers(
            () -> faker.name().firstName(), 
            () -> faker.name().lastName())
        .minLen(3)
        .maxLen(5)
        .build().get();

A list can also contain different types:

Java

List<Object> objects = 
    faker.collection()
        .suppliers(
            () -> faker.name().firstName(), 
            () -> faker.random().nextInt(100))
        .maxLen(5)
        .build().get();

With usage of nullRate it is possible to specify how often it should contain null values. By default, it's value is 0, i.e. no null values will be generated.

Java

List<Object> objects = 
    faker.collection()
        .suppliers(
            () -> faker.name().firstName(), 
            () -> faker.random().nextInt(100))
        .nullRate(1)
        .maxLen(5)
        .build().get();

will generate a collection where every value is null. And to generate a collection with only about 30% values of null nullRate(0.3) will do it

Java

List<Object> objects = 
    faker.collection()
        .suppliers(
            () -> faker.name().firstName(), 
            () -> faker.random().nextInt(100))
        .nullRate(0.3)
        .maxLen(5)
        .build().get();